As wireless communications technology continues to evolve, there is a focus on improving both reliability and speed. In recent years, technologies such as multiple-input-multiple-output (MIMO) and carrier aggregation have been used to increase both speed and reliability of a wireless connection. At a high level, MIMO and carrier aggregation allow multiple radio frequency (RF) signals to be simultaneously transmitted and/or received by a device. In the case of carrier aggregation, RF signals within different RF operating bands, different carriers within a single RF operating band, or both are simultaneously transmitted and then separated by a receiving device to obtain the data therein. Different data may be transmitted over each RF operating band and/or each carrier within a single RF operating band, thus increasing data throughput. In the case of MIMO, different RF signals are transmitted at the same frequency (e.g., by using spatial diversity) and then separated by a receiving device to obtain the data therein. The different RF signals may each carry different data, thereby increasing data throughput.
RF front end circuitry is generally responsible for processing received RF signals in order to support MIMO and/or carrier aggregation. In particular, RF filtering circuitry within the RF front end circuitry must be capable of separating received RF signals such that the data included therein can be obtained. To support carrier aggregation, the RF filtering circuitry must be capable of separating RF signals within different RF operating bands and/or different carriers within a single operating band. To support MIMO, the RF filtering circuitry must be capable of separating spatially diverse RF signals at the same frequency from one another. Generally, supporting carrier aggregation requires several grouped filters (i.e., multiplexers), where each grouped filter is configured to separate certain combinations of RF signals within different operating bands or RF signals within different carriers of the same operating band. Supporting MIMO generally requires a separate filter for each MIMO data stream, where each filter is configured to isolate RF signals at a particular RF frequency or a relatively small range of RF frequencies. Generally, filters used for carrier aggregation and filters used for MIMO are provided separately, thereby increasing the total number of filters in RF front end circuitry supporting both modes. As the number of carrier aggregation and/or MIMO modes supported by RF front end circuitry increases, the number of filters required for supporting these modes may quickly become impractical due to the area and insertion loss associated therewith.
In light of the above, there is a need for improved RF front end circuitry capable of supporting both MIMO and carrier aggregation modes while reducing the complexity of RF filtering circuitry used therein.